Dad rolls his eyes and calls it "separation anxiety" and when Mommy isn't looking Ichigo sticks his tongue out at him. He doesn't know what separation anxiety means and Dad looks like he's going to start crying out of sheer frustration every time he does that, but Ichigo knows when he's been mocked.

No, Ichigo doesn't like to be away from his mother, not for any length of time. It's noticed, commented on, and ignored. After all, is it really so odd that a small boy doesn't want to be away from his mother? No, it really isn't.

It's not odd, but Isshin's right when he calls it "separation anxiety". Ichigo's visibly nervous when Masaki sees him off to school; once he's home he's practically walking on her heels. When Masaki has to go into the next room Ichigo immediately runs after her.